機(jī)械類畢業(yè)設(shè)計(jì)外文翻譯---軸承的摩擦與潤(rùn)滑-全文預(yù)覽
【正文】 s and under varying load conditions . the journal bearings used in the steam turbines of power generating station is said to have reliabilities approaching 100 percent. At the other extreme there are thousands of applications in which the loads are light and the service relatively unimportant. a simple ,easily installed bearing is required ,suing little or no lubrication. In such cases an antifriction bearing might be a poor answer because because of the cost, the close ,the radial space required ,or the increased inertial effects. Recent metallurgy developments in bearing materials , bined with increased knowledge of the lubrication process, now make it possible to design journal bearings with satisfactory lives and very good reliabilities. 7 中文譯文： 軸承的摩擦與潤(rùn)滑 現(xiàn)在看來(lái)，有很多這種情況，許多學(xué)生在被問(wèn)到關(guān)于摩擦的問(wèn)題時(shí)，往往都沒(méi)引起足夠的重視，甚至是忽視它。 even some metals monly serve as sliding surfaces in some sophisticated machines. Function of lubricants 4 Although a lubricant primarily controls friction and ordinarily does perform numerous other functions, which vary with the application and usually are interrelated . Friction control. The amount and character of the lubricant made available to sliding surfaces have a profound effect upon the friction that is encountered. For example, disregarding such related factors as heat and wear but considering friction alone between the same surfaces with on lubricant. Under fluidfilm conditions, friction is encountered. In a great range of viscosities and thus can satisfy a broad spectrum of functional requirements. Under boundary lubrication conditions , the effect of viscosity on friction bees less significant than the chemical nature of the lubricant. Wear control. wear occurs on lubricated surfaces by abrasion, corrosion ,and solidtosolid contact wear by providing a film that increases the distance between the sliding surfaces ,thereby lessening the damage by abrasive contaminants and surface asperities. Temperature control. Lubricants assist in controlling corrosion of the surfaces themselves is twofold. When machinery is idle, the lubricant acts as a preservative. When machinery is in use, the lubricant controls corrosion by coating lubricated parts with a protective film that may contain additives to neutralize corrosive materials. The ability of a lubricant to control corrosion is directly relatly to the thickness of the lubricant film remaining on the metal surfaces and the chermical position of the lubricant. Other functions Lubrication are frequently used for purposes other than the reduction of friction. Some of these applications are described below. Power transmission. Lubricants are widely employed as hydraulic fluids in fluid transmission devices. Insulation. In specialized applications such as transformers and switchgear , lubricants with high dielectric constants acts as electrical insulators. For maximum insulating properties, a lubricant must be kept free of contaminants and water. 5 Shock dampening. Lubricants act as shockdampening fluids in energy transferring devices such as shock absorbers and around machine parts such as gears that are subjected to high intermittent loads. Sealing. Lubricating grease frequently performs the special function of forming a seal to retain lubricants or to exclude contaminants. The object of lubrication is to reduce friction ,wear , and heating of machine pars which move relative to each other. A lubricant is any substance which, when inserted between the moving surfaces, acplishes these purposes. Most lubricants are l
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